Hi, I am trying to recover from the loss of a control file (which is multiplexed). I am on Oracle 10g, implementing FRA and a recovery catalog. We have taken a most recent hot backup this morning. I have performed the following steps:

Kind of expected behavior (based on the partial session you have posted with only commands and no output is included) as you broke all basic rules.
Quoting Docs

If you want to restore the control file from autobackup, the database must be in a NOMOUNT state.
You must first set the DBID for your database, and then use the RESTORE CONTROLFILE FROM AUTOBACKUP command:

>>You dont have to use DBid if you are in 10g, have FRA set up and configured controlfile autobackup on.
Kind of right.
But you are trying to restore using "from autobackup" which may not work. In NOMOUNT state
try